Abstract
The Barberton Greenstone Belt (BGB), South Africa, consists of volcano-sedimentary and sedimentary successions deposited between 3.5 and 3.2Ga, which are subdivided into three groups: the Onverwacht, Fig Tree, and Moodies. After deposition, the Barberton Greenstone Belt underwent relatively low-grade tectonothermal events, enabling estimation of surface environmental events and biological evolution in the Middle Archean. Isotopic studies suggest the activity of methanogen, sulfate-reducing bacteria, and photosynthetic bacteria at 3.4Ga. Microbial dissimilatory iron reduction (DIR) is also considered one of the earliest expressions of metabolism on Earth, but the isotopic signal of microbial DIR is still uncertain in the Archean. We performed in-situ iron isotope analyses of individual pyrites in sedimentary rocks from the BGB, using a femtosecond laser ablation multi-collector ICP-MS technique (fs-LA-MC-ICP-MS) to find isotopic evidence for the microbial activity. We obtained a large variation in δ56Fe values, ranging from -1.84 to +3.79‰. Most of the δ56Fe values of pyrites from the Hooggenoeg Complex show positive values, whereas those from the Noisy Complex and subsequent sedimentary sequences show a wide variation from negative to positive δ56Fe values. One of the main differences between these complexes is their depositional depth. The Hooggenoeg Complex was probably deposited in a deep-ocean environment, whereas the Noisy Complex was in shallow water. The negative δ56Fe values of pyrite grains in the Noisy Complex, Onverwacht Group indicate the occurrence of partial reduction caused by microbial DIR in a Middle Archean shallow sea.
| Original language | English |
|---|---|
| Pages (from-to) | 58-73 |
| Number of pages | 16 |
| Journal | Chemical Geology |
| Volume | 403 |
| DOIs | |
| Publication status | Published - May 8 2015 |
| Externally published | Yes |
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Keywords
- Barberton Greenstone Belt (BGB)
- Iron isotope geochemistry
- Microbial dissimilatory iron reduction (DIR)
- Middle Archean
- Pyrite
ASJC Scopus subject areas
- Geochemistry and Petrology
- Geology
Cite this
In-situ iron isotope analyses of pyrites from 3.5 to 3.2Ga sedimentary rocks of the Barberton Greenstone Belt, Kaapvaal Craton. / Yoshiya, Kazumi; Sawaki, Yusuke; Shibuya, Takazo; Yamamoto, Shinji; Komiya, Tsuyoshi; Hirata, Takafumi; Maruyama, Shigenori.
In: Chemical Geology, Vol. 403, 08.05.2015, p. 58-73.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - In-situ iron isotope analyses of pyrites from 3.5 to 3.2Ga sedimentary rocks of the Barberton Greenstone Belt, Kaapvaal Craton
AU - Yoshiya, Kazumi
AU - Sawaki, Yusuke
AU - Shibuya, Takazo
AU - Yamamoto, Shinji
AU - Komiya, Tsuyoshi
AU - Hirata, Takafumi
AU - Maruyama, Shigenori
PY - 2015/5/8
Y1 - 2015/5/8
N2 - The Barberton Greenstone Belt (BGB), South Africa, consists of volcano-sedimentary and sedimentary successions deposited between 3.5 and 3.2Ga, which are subdivided into three groups: the Onverwacht, Fig Tree, and Moodies. After deposition, the Barberton Greenstone Belt underwent relatively low-grade tectonothermal events, enabling estimation of surface environmental events and biological evolution in the Middle Archean. Isotopic studies suggest the activity of methanogen, sulfate-reducing bacteria, and photosynthetic bacteria at 3.4Ga. Microbial dissimilatory iron reduction (DIR) is also considered one of the earliest expressions of metabolism on Earth, but the isotopic signal of microbial DIR is still uncertain in the Archean. We performed in-situ iron isotope analyses of individual pyrites in sedimentary rocks from the BGB, using a femtosecond laser ablation multi-collector ICP-MS technique (fs-LA-MC-ICP-MS) to find isotopic evidence for the microbial activity. We obtained a large variation in δ56Fe values, ranging from -1.84 to +3.79‰. Most of the δ56Fe values of pyrites from the Hooggenoeg Complex show positive values, whereas those from the Noisy Complex and subsequent sedimentary sequences show a wide variation from negative to positive δ56Fe values. One of the main differences between these complexes is their depositional depth. The Hooggenoeg Complex was probably deposited in a deep-ocean environment, whereas the Noisy Complex was in shallow water. The negative δ56Fe values of pyrite grains in the Noisy Complex, Onverwacht Group indicate the occurrence of partial reduction caused by microbial DIR in a Middle Archean shallow sea.
AB - The Barberton Greenstone Belt (BGB), South Africa, consists of volcano-sedimentary and sedimentary successions deposited between 3.5 and 3.2Ga, which are subdivided into three groups: the Onverwacht, Fig Tree, and Moodies. After deposition, the Barberton Greenstone Belt underwent relatively low-grade tectonothermal events, enabling estimation of surface environmental events and biological evolution in the Middle Archean. Isotopic studies suggest the activity of methanogen, sulfate-reducing bacteria, and photosynthetic bacteria at 3.4Ga. Microbial dissimilatory iron reduction (DIR) is also considered one of the earliest expressions of metabolism on Earth, but the isotopic signal of microbial DIR is still uncertain in the Archean. We performed in-situ iron isotope analyses of individual pyrites in sedimentary rocks from the BGB, using a femtosecond laser ablation multi-collector ICP-MS technique (fs-LA-MC-ICP-MS) to find isotopic evidence for the microbial activity. We obtained a large variation in δ56Fe values, ranging from -1.84 to +3.79‰. Most of the δ56Fe values of pyrites from the Hooggenoeg Complex show positive values, whereas those from the Noisy Complex and subsequent sedimentary sequences show a wide variation from negative to positive δ56Fe values. One of the main differences between these complexes is their depositional depth. The Hooggenoeg Complex was probably deposited in a deep-ocean environment, whereas the Noisy Complex was in shallow water. The negative δ56Fe values of pyrite grains in the Noisy Complex, Onverwacht Group indicate the occurrence of partial reduction caused by microbial DIR in a Middle Archean shallow sea.
KW - Barberton Greenstone Belt (BGB)
KW - Iron isotope geochemistry
KW - Microbial dissimilatory iron reduction (DIR)
KW - Middle Archean
KW - Pyrite
UR - http://www.scopus.com/inward/record.url?scp=84924394659&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84924394659&partnerID=8YFLogxK
U2 - 10.1016/j.chemgeo.2015.03.007
DO - 10.1016/j.chemgeo.2015.03.007
M3 - Article
AN - SCOPUS:84924394659
VL - 403
SP - 58
EP - 73
JO - Chemical Geology
JF - Chemical Geology
SN - 0009-2541
ER -